Question

Over the counter cold medications are complex mixtures that contain a combination of active ingredients that have specific effects. These mixtures are routinely analysed via high performance liquid chromatography (HPLC) to verify that the concentration of active ingredients are consistent to guidelines A cough mixture containing phenylephrine hydrochloride (decongestant) and chlorpheneramine maleate (antihistamine) was run on a HPLC with the parameters shown below Gemini C18 (150 x 4.6 mm, 5 ?m) HPLC column 1.0 mL/min UV-VIS at 215nm Column Flow rate Detection However, the optimal composition of the mobile phase for effective separation of the two active ingredients needs to be determined. As the analytical scientist you must decide which mobile phase composition will be used Below are the tabulated data from 2 different mobile phase methods that were tested Isocratic elution: acetonitrile methanol phosphate buffer 50: 20 30, v/v/v, pH 5.6 Analyte Retention time Peak width at (tR) (min) base (W1/2) min henylephrine hvdrochloride 1.5 maleate 4.5 n/a 0.89 0.90 Isocratic elution: acetonitrile methanol phosphate buffer 40: 10: 50, v/v/v, pH 5.6 Analyte Retention time Peak width at (tR)(min) base (W1/2) min n/a 0.66 0.90 henylephrine hydrochloride 2.81 maleate 3.21 (a) Using the data above, determine which mobile phase composition would be best for the analysis of the phenylephrine hydrochloride and chlorpheneramine maleate and explain why (b) As part of the method development stage, the resolution is closely monitored to ensure that optimum separation has occurred. Using the resolution equation, explain how resolution in HPLC can be optimised

Answer 1

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